8 BULLETIN 48, UNITED STATES NATIONAL MUSEUM. 



really <^reatly elongated scales, the shank l)eing a very attenuated 

 cylinder, while the tip is sometimes dilated, club like, and sometimes 

 fan-like, but never very much enlarged. The shorter they become the 

 more distinct is the scaly character of these pencils; l)ut for conven- 

 ience and as expressive of their actual ap[)jearance they will be referred 

 to as tufts or pencils of hair. 



The femur in this tribe is quite usually sujjplied with a pencil of long- 

 hair, attached to the upi)er side near tlie tip and lying in a groove 

 which includes nearly all there is of the femur. In length this ])en- 

 cil equals the tr(Hdianter and lemur combined, and ^\hen at rest it 

 folds back, the femur is applied to the coxa, and the groove is thus 

 closed. By this application of the femoral groove to the groove in the 

 coxa the pencils of hair on these parts lie together in what is then a 

 closed cylinder or elongated capsule. AMien the leg is extended the 

 femoral pencil may be erected and expanded fiin-like, lormiug in many 

 cases more than three-fourths of a comjilete disk. The tibial process 

 quite frequently covers another pencil of similar hair which, while it 

 may be dilated, spreads out loosely in all directions and not fan like. 

 Quite usually, when no distinct pencil of hair is present, the }>rocess 

 covers a loose mass of specialized shorter scales, while huge scales 

 fringe the edges of the process. The latter folds around the elongated 

 tlrst tarsal joint, which is often grooved to conceal or protect the tibial 

 tuft, ^o tutts of hair or scales are on the tarsi. 



A si)eciineii with its fore legs extended and all the pencils of hair 

 expanded is a curious and interesting sight. ZancJofinntha la ciguia 

 and Chyiolitu morhidaJis, both common species, have these tuftings well 

 develoi)ed. 



What purpose do these structures serve? That they are sensory is 

 reasonably certain, from the facts that they are connected with special- 

 ized pittings and are so carefully i^rovided with protective coverings 

 when not in actual use. In iny earlier w^ritings I called them " scent 

 organs," following those German authors who consider them " Duft 

 apparate." The suggestion is, that certain glands connected with 

 these pencils secrete some substance which is odorous and which 

 through the pittings or pores of the integument bring their secretions 

 into contact with the pencils of hair, by means of which the odor is 

 gradually diffused. That this odor is connected Avith the sexual func- 

 tion is universally assumed; but just how, is not so clear. It can not 

 be that the odor is meant to attract the female, for the attraction is the 

 other way, and the male seeks out the opposite sex. If the tutts came 

 into play in courting it would seem as though there should be some 

 corresponding organ for the appreciations of the odors m the female; 

 but I have entirely failed to find any such. In actual copulation there 

 seems no function that could be filled by these structures. They must 

 be, for the present, classed among those appendages with the use of 

 which we are not fully acquainted. It is indeed remarkable that 



